I grew Pink Sunday this year as well. It struggled. If you got it established, it would sit there in the heat (fs) and wither. Irregardless of how much watering you did. I learned do not transplant these any bigger than 6". They died if I did. They are also meant for partial shade. Ok, not in Oklahoma. The ones I had in partial shade did not fare as well as the full sun ones. They reminded me of how snapdragons will do in heat. They bloomed for one month and then promptly died. Their color also depended on the heat. I had one that made it past the heat and it now blooms much deeper than the one that struggled and was merely a light pink. I would still plant this again but just not next year.
I also planted the Blue Monday with it. It did the same way as the pink sunday. Not a bad combination but I'm really thinking maybe this plant would do better in a cooler climate?